#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H

#include<stdio.h>
#include<stdbool.h>  //bool

// 从Linux内核list.h复制的双向链表实现
// 这是Linux内核中广泛使用的双向链表数据结构
//  container_of
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:	the pointer to the member.
 * @type:	the type of the container struct this is embedded in.
 * @member:	the name of the member within the struct.
 *
 */
#define container_of(ptr, type, member) ({			\
	const typeof(((type *)0)->member) * __mptr = (ptr);	\
	(type *)((char *)__mptr - offsetof(type, member)); })

/**
 * struct list_head - 双向链表节点结构
 * @next: 指向下一个节点的指针
 * @prev: 指向前一个节点的指针
 * 
 * 这是Linux内核中双向链表的基本结构，通过嵌入到其他结构体中使用
 * 例如：
 * struct my_struct {
 *     int data;
 *     struct list_head list;
 * };
 */
struct list_head {
	struct list_head *next, *prev;
};
/**
 * struct hlist_head - 哈希链表头结构
 * @first: 指向第一个节点的指针
 * 
 * 用于哈希表实现，相比list_head节省一个指针的空间
 */
struct hlist_head {
	struct hlist_node *first;
};

/**
 * struct hlist_node - 哈希链表节点结构
 * @next: 指向下一个节点的指针
 * @pprev: 指向前一个节点的next指针的地址
 * 
 * 用于构建哈希链表，相比list_node节省一个指针的空间
 */
struct hlist_node {
	struct hlist_node *next, **pprev;
};

/**
 * LIST_HEAD_INIT - 初始化链表头的宏
 * @name: 链表头名称
 * 
 * 初始化链表头，使next和prev都指向自己
 */
#define LIST_HEAD_INIT(name) { &(name), &(name) }

/**
 * LIST_HEAD - 定义并初始化链表头的宏
 * @name: 链表头名称
 * 
 * 静态初始化一个链表头，通常在全局变量定义时使用
 */
#define LIST_HEAD(name) \
	struct list_head name = LIST_HEAD_INIT(name)

/**
 * INIT_LIST_HEAD - 初始化链表头的函数
 * @list: 要初始化的链表头指针
 * 
 * 运行时动态初始化链表头，使链表头的next和prev都指向自己
 * 通常在动态分配的结构体中使用
 */
static inline void INIT_LIST_HEAD(struct list_head *list)
{
	list->next = list;
	list->prev = list;
}

#ifdef CONFIG_DEBUG_LIST
/**
 * __list_add_valid - 验证链表添加操作的有效性(调试用)
 * @new: 要添加的新节点
 * @prev: 前一个节点
 * @next: 后一个节点
 * 
 * 返回: 如果添加操作有效返回true，否则返回false
 */
extern bool __list_add_valid(struct list_head *new,
			      struct list_head *prev,
			      struct list_head *next);

/**
 * __list_del_entry_valid - 验证链表删除操作的有效性(调试用)
 * @entry: 要删除的节点
 * 
 * 返回: 如果删除操作有效返回true，否则返回false
 */
extern bool __list_del_entry_valid(struct list_head *entry);
#else
/**
 * __list_add_valid - 空实现(非调试版本)
 */
static inline bool __list_add_valid(struct list_head *new,
				struct list_head *prev,
				struct list_head *next)
{
	return true;
}

/**
 * __list_del_entry_valid - 空实现(非调试版本)
 */
static inline bool __list_del_entry_valid(struct list_head *entry)
{
	return true;
}
#endif

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
/*
 * __list_add - 在两个已知连续节点之间插入新节点(内部函数)
 * @new: 要插入的新节点
 * @prev: 前一个节点
 * @next: 后一个节点
 *
 * 这是一个底层操作，仅在已知prev和next节点时使用
 */
static inline void __list_add(struct list_head *new,
			      struct list_head *prev,
			      struct list_head *next)
{
	if (!__list_add_valid(new, prev, next))
		return;

	next->prev = new;
	new->next = next;
	new->prev = prev;
	prev->next = new;
}

/**
 * list_add - add a new entry
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
/**
 * list_add - 在链表头部添加新节点
 * @new: 要添加的新节点
 * @head: 链表头
 *
 * 将新节点插入到链表头部，适合实现栈结构
 */
static inline void list_add(struct list_head *new, struct list_head *head)
{
	__list_add(new, head, head->next);
}


/**
 * list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
/**
 * list_add_tail - 在链表尾部添加新节点
 * @new: 要添加的新节点
 * @head: 链表头
 *
 * 将新节点插入到链表尾部，适合实现队列结构
 */
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
	__list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
/*
 * __list_del - 通过使prev/next指向彼此来删除链表条目(内部函数)
 * @prev: 要删除节点的前一个节点
 * @next: 要删除节点的后一个节点
 */
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
	next->prev = prev;
}

/**
 * list_del - deletes entry from list.
 * @entry: the element to delete from the list.
 * Note: list_empty() on entry does not return true after this, the entry is
 * in an undefined state.
 */
static inline void __list_del_entry(struct list_head *entry)
{
	if (!__list_del_entry_valid(entry))
		return;

	__list_del(entry->prev, entry->next);
}

/**
 * list_del - 从链表中删除一个节点
 * @entry: 要删除的节点
 *
 * 注意: 删除后节点处于未定义状态，list_empty()可能不会返回true
 * 删除后节点的next和prev指针被置为NULL，防止误用
 */
static inline void list_del(struct list_head *entry)
{
	__list_del_entry(entry);
	entry->next = NULL;
	entry->prev = NULL;
}

/**
 * list_replace - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * If @old was empty, it will be overwritten.
 */
/**
 * list_replace - 用新节点替换旧节点
 * @old: 要被替换的旧节点
 * @new: 用来替换的新节点
 *
 * 如果@old为空，它将被覆盖
 */
static inline void list_replace(struct list_head *old,
				struct list_head *new)
{
	new->next = old->next;
	new->next->prev = new;
	new->prev = old->prev;
	new->prev->next = new;
}

/**
 * list_replace_init - 用新节点替换旧节点并初始化旧节点
 * @old: 要被替换的旧节点
 * @new: 用来替换的新节点
 *
 * 用新节点替换旧节点后，将旧节点初始化为空链表
 */
static inline void list_replace_init(struct list_head *old,
					struct list_head *new)
{
	list_replace(old, new);
	INIT_LIST_HEAD(old);
}

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void list_del_init(struct list_head *entry)
{
	__list_del_entry(entry);
	INIT_LIST_HEAD(entry);
}

/**
 * list_move - delete from one list and add as another's head
 * @list: the entry to move
 * @head: the head that will precede our entry
 */
/**
 * list_move - 将节点从一个链表移动到另一个链表头部
 * @list: 要移动的节点
 * @head: 目标链表的头部
 *
 * 先从原链表中删除节点，然后添加到目标链表头部
 */
static inline void list_move(struct list_head *list, struct list_head *head)
{
	__list_del_entry(list);
	list_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another's tail
 * @list: the entry to move
 * @head: the head that will follow our entry
 */
/**
 * list_move_tail - 将节点从一个链表移动到另一个链表尾部
 * @list: 要移动的节点
 * @head: 目标链表的头部
 *
 * 先从原链表中删除节点，然后添加到目标链表尾部
 */
static inline void list_move_tail(struct list_head *list,
				  struct list_head *head)
{
	__list_del_entry(list);
	list_add_tail(list, head);
}

/**
 * list_bulk_move_tail - move a subsection of a list to its tail
 * @head: the head that will follow our entry
 * @first: first entry to move
 * @last: last entry to move, can be the same as first
 *
 * Move all entries between @first and including @last before @head.
 * All three entries must belong to the same linked list.
 */
static inline void list_bulk_move_tail(struct list_head *head,
				       struct list_head *first,
				       struct list_head *last)
{
	first->prev->next = last->next;
	last->next->prev = first->prev;

	head->prev->next = first;
	first->prev = head->prev;

	last->next = head;
	head->prev = last;
}

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
/**
 * list_is_last - 测试节点是否是链表的最后一个节点
 * @list: 要测试的节点
 * @head: 链表头
 *
 * 返回: 如果是最后一个节点返回1，否则返回0
 */
static inline int list_is_last(const struct list_head *list,
				const struct list_head *head)
{
	return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
/**
 * list_empty - 测试链表是否为空
 * @head: 链表头
 *
 * 返回: 链表为空返回1，否则返回0
 */
static inline int list_empty(const struct list_head *head)
{
	return head->next == head;
}

/**
 * list_empty_careful - tests whether a list is empty and not being modified
 * @head: the list to test
 *
 * Description:
 * tests whether a list is empty _and_ checks that no other CPU might be
 * in the process of modifying either member (next or prev)
 *
 * NOTE: using list_empty_careful() without synchronization
 * can only be safe if the only activity that can happen
 * to the list entry is list_del_init(). Eg. it cannot be used
 * if another CPU could re-list_add() it.
 */
/**
 * list_empty_careful - 谨慎测试链表是否为空
 * @head: 链表头
 *
 * 在并发环境下更安全的链表空测试，检查next和prev指针是否一致
 * 返回: 链表为空返回1，否则返回0
 */
static inline int list_empty_careful(const struct list_head *head)
{
	struct list_head *next = head->next;
	return (next == head) && (next == head->prev);
}

/**
 * list_rotate_left - rotate the list to the left
 * @head: the head of the list
 */
/**
 * list_rotate_left - 将链表向左旋转(第一个节点移动到末尾)
 * @head: 链表头
 *
 * 如果链表不为空，将第一个节点移动到链表末尾
 */
static inline void list_rotate_left(struct list_head *head)
{
	struct list_head *first;

	if (!list_empty(head)) {
		first = head->next;
		list_move_tail(first, head);
	}
}

/**
 * list_is_singular - tests whether a list has just one entry.
 * @head: the list to test.
 */
/**
 * list_is_singular - 测试链表是否只有一个节点
 * @head: 链表头
 *
 * 返回: 如果链表只有一个节点返回1，否则返回0
 */
static inline int list_is_singular(const struct list_head *head)
{
	return !list_empty(head) && (head->next == head->prev);
}

/*
 * __list_cut_position - 在指定位置切割链表(内部函数)
 * @list: 新链表头，用于存放切割出的部分
 * @head: 原链表头
 * @entry: 切割位置节点
 *
 * 将原链表从entry节点处切割，entry之前的部分放入新链表
 */
static inline void __list_cut_position(struct list_head *list,
		struct list_head *head, struct list_head *entry)
{
	struct list_head *new_first = entry->next;
	list->next = head->next;
	list->next->prev = list;
	list->prev = entry;
	entry->next = list;
	head->next = new_first;
	new_first->prev = head;
}

/**
 * list_cut_position - cut a list into two
 * @list: a new list to add all removed entries
 * @head: a list with entries
 * @entry: an entry within head, could be the head itself
 *	and if so we won't cut the list
 *
 * This helper moves the initial part of @head, up to and
 * including @entry, from @head to @list. You should
 * pass on @entry an element you know is on @head. @list
 * should be an empty list or a list you do not care about
 * losing its data.
 *
 */
/**
 * list_cut_position - 在指定位置切割链表
 * @list: 新链表头，用于存放切割出的部分
 * @head: 原链表头
 * @entry: 切割位置节点
 *
 * 将原链表从entry节点处切割，entry之前的部分放入新链表
 * 处理各种边界条件，如空链表、单节点链表等
 */
static inline void list_cut_position(struct list_head *list,
		struct list_head *head, struct list_head *entry)
{
	if (list_empty(head))
		return;
	if (list_is_singular(head) &&
		(head->next != entry && head != entry))
		return;
	if (entry == head)
		INIT_LIST_HEAD(list);
	else
		__list_cut_position(list, head, entry);
}

/**
 * list_cut_before - cut a list into two, before given entry
 * @list: a new list to add all removed entries
 * @head: a list with entries
 * @entry: an entry within head, could be the head itself
 *
 * This helper moves the initial part of @head, up to but
 * excluding @entry, from @head to @list.  You should pass
 * in @entry an element you know is on @head.  @list should
 * be an empty list or a list you do not care about losing
 * its data.
 * If @entry == @head, all entries on @head are moved to
 * @list.
 */
/**
 * list_cut_before - 在指定节点前切割链表
 * @list: 新链表头，用于存放切割出的部分
 * @head: 原链表头
 * @entry: 切割位置节点
 *
 * 将原链表在entry节点前切割，entry之前的部分(不包括entry)放入新链表
 */
static inline void list_cut_before(struct list_head *list,
				   struct list_head *head,
				   struct list_head *entry)
{
	if (head->next == entry) {
		INIT_LIST_HEAD(list);
		return;
	}
	list->next = head->next;
	list->next->prev = list;
	list->prev = entry->prev;
	list->prev->next = list;
	head->next = entry;
	entry->prev = head;
}

/*
 * __list_splice - 拼接两个链表(内部函数)
 * @list: 要拼接的链表
 * @prev: 拼接位置的前一个节点
 * @next: 拼接位置的后一个节点
 *
 * 将list链表拼接到prev和next节点之间
 */
static inline void __list_splice(const struct list_head *list,
				 struct list_head *prev,
				 struct list_head *next)
{
	struct list_head *first = list->next;
	struct list_head *last = list->prev;

	first->prev = prev;
	prev->next = first;

	last->next = next;
	next->prev = last;
}

/**
 * list_splice - join two lists, this is designed for stacks
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
/**
 * list_splice - 将链表拼接到另一个链表头部
 * @list: 要拼接的链表
 * @head: 目标链表的头部
 *
 * 将list链表拼接到head链表头部，适合实现栈结构
 */
static inline void list_splice(const struct list_head *list,
				struct list_head *head)
{
	if (!list_empty(list))
		__list_splice(list, head, head->next);
}

/**
 * list_splice_tail - join two lists, each list being a queue
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
/**
 * list_splice_tail - 将链表拼接到另一个链表尾部
 * @list: 要拼接的链表
 * @head: 目标链表的头部
 *
 * 将list链表拼接到head链表尾部，适合实现队列结构
 */
static inline void list_splice_tail(struct list_head *list,
				struct list_head *head)
{
	if (!list_empty(list))
		__list_splice(list, head->prev, head);
}

/**
 * list_splice_init - join two lists and reinitialise the emptied list.
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * The list at @list is reinitialised
 */
/**
 * list_splice_init - 拼接链表并初始化原链表
 * @list: 要拼接的链表
 * @head: 目标链表的头部
 *
 * 将list链表拼接到head链表头部，然后将list链表初始化为空
 */
static inline void list_splice_init(struct list_head *list,
				    struct list_head *head)
{
	if (!list_empty(list)) {
		__list_splice(list, head, head->next);
		INIT_LIST_HEAD(list);
	}
}

/**
 * list_splice_tail_init - join two lists and reinitialise the emptied list
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * Each of the lists is a queue.
 * The list at @list is reinitialised
 */
/**
 * list_splice_tail_init - 拼接链表到尾部并初始化原链表
 * @list: 要拼接的链表
 * @head: 目标链表的头部
 *
 * 将list链表拼接到head链表尾部，然后将list链表初始化为空
 */
static inline void list_splice_tail_init(struct list_head *list,
					 struct list_head *head)
{
	if (!list_empty(list)) {
		__list_splice(list, head->prev, head);
		INIT_LIST_HEAD(list);
	}
}

/**
 * list_entry - get the struct for this entry
 * @ptr:	the &struct list_head pointer.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 */
/**
 * list_entry - 获取包含链表节点的结构体
 * @ptr:    list_head指针
 * @type:   包含list_head的结构体类型
 * @member: list_head在结构体中的成员名
 *
 * 通过链表节点指针获取包含它的外层结构体指针
 */
#define list_entry(ptr, type, member) \
	container_of(ptr, type, member)

/**
 * list_first_entry - get the first element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
	list_entry((ptr)->next, type, member)

/**
 * list_last_entry - get the last element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_last_entry(ptr, type, member) \
	list_entry((ptr)->prev, type, member)

/**
 * list_first_entry_or_null - get the first element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_head within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) ({ \
	struct list_head *head__ = (ptr); \
	struct list_head *pos__ = READ_ONCE(head__->next); \
	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
})

/**
 * list_next_entry - get the next element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_next_entry(pos, member) \
	list_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * list_prev_entry - get the prev element in list
 * @pos:	the type * to cursor
 * @member:	the name of the list_head within the struct.
 */
#define list_prev_entry(pos, member) \
	list_entry((pos)->member.prev, typeof(*(pos)), member)

/**
 * list_for_each	-	iterate over a list
 * @pos:	the &struct list_head to use as a loop cursor.
 * @head:	the head for your list.
 */
/**
 * list_for_each - 正向遍历链表
 * @pos:    用作循环游标的list_head指针
 * @head:   链表头
 *
 * 从头到尾遍历链表，不安全的遍历方式(遍历时不能删除节点)
 */
#define list_for_each(pos, head) \
	for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * list_for_each_prev	-	iterate over a list backwards
 * @pos:	the &struct list_head to use as a loop cursor.
 * @head:	the head for your list.
 */
#define list_for_each_prev(pos, head) \
	for (pos = (head)->prev; pos != (head); pos = pos->prev)

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
/**
 * list_for_each_safe - 安全的正向遍历链表
 * @pos:    用作循环游标的list_head指针
 * @n:      另一个list_head指针用作临时存储
 * @head:   链表头
 *
 * 安全的遍历方式，可以在遍历时删除节点
 */
#define list_for_each_safe(pos, n, head) \
	for (pos = (head)->next, n = pos->next; pos != (head); \
		pos = n, n = pos->next)

/**
 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_prev_safe(pos, n, head) \
	for (pos = (head)->prev, n = pos->prev; \
	     pos != (head); \
	     pos = n, n = pos->prev)

/**
 * list_for_each_entry	-	iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
/**
 * list_for_each_entry - 遍历包含链表节点的结构体
 * @pos:    用作循环游标的结构体指针
 * @head:   链表头
 * @member: list_head在结构体中的成员名
 *
 * 遍历链表并获取每个节点所在的外层结构体
 */
#define list_for_each_entry(pos, head, member)				\
	for (pos = list_first_entry(head, typeof(*pos), member);	\
	     &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)			\
	for (pos = list_last_entry(head, typeof(*pos), member);		\
	     &pos->member != (head); 					\
	     pos = list_prev_entry(pos, member))

/**
 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
 * @pos:	the type * to use as a start point
 * @head:	the head of the list
 * @member:	the name of the list_head within the struct.
 *
 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
 */
#define list_prepare_entry(pos, head, member) \
	((pos) ? : list_entry(head, typeof(*pos), member))

/**
 * list_for_each_entry_continue - continue iteration over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member) 		\
	for (pos = list_next_entry(pos, member);			\
	     &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member)		\
	for (pos = list_prev_entry(pos, member);			\
	     &pos->member != (head);					\
	     pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member) 			\
	for (; &pos->member != (head);					\
	     pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_from_reverse - iterate backwards over list of given type
 *                                    from the current point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, continuing from current position.
 */
#define list_for_each_entry_from_reverse(pos, head, member)		\
	for (; &pos->member != (head);					\
	     pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 */
/**
 * list_for_each_entry_safe - 安全的遍历包含链表节点的结构体
 * @pos:    用作循环游标的结构体指针
 * @n:      另一个结构体指针用作临时存储
 * @head:   链表头
 * @member: list_head在结构体中的成员名
 *
 * 安全的遍历方式，可以在遍历时删除节点
 */
#define list_for_each_entry_safe(pos, n, head, member)			\
	for (pos = list_first_entry(head, typeof(*pos), member),	\
		n = list_next_entry(pos, member);			\
	     &pos->member != (head); 					\
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member) 		\
	for (pos = list_next_entry(pos, member), 				\
		n = list_next_entry(pos, member);				\
	     &pos->member != (head);						\
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 */
#define list_for_each_entry_safe_from(pos, n, head, member) 			\
	for (n = list_next_entry(pos, member);					\
	     &pos->member != (head);						\
	     pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member)		\
	for (pos = list_last_entry(head, typeof(*pos), member),		\
		n = list_prev_entry(pos, member);			\
	     &pos->member != (head); 					\
	     pos = n, n = list_prev_entry(n, member))

/**
 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
 * @pos:	the loop cursor used in the list_for_each_entry_safe loop
 * @n:		temporary storage used in list_for_each_entry_safe
 * @member:	the name of the list_head within the struct.
 *
 * list_safe_reset_next is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 */
#define list_safe_reset_next(pos, n, member)				\
	n = list_next_entry(pos, member)

/*
 * Double linked lists with a single pointer list head.
 * Mostly useful for hash tables where the two pointer list head is
 * too wasteful.
 * You lose the ability to access the tail in O(1).
 */

#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
static inline void INIT_HLIST_NODE(struct hlist_node *h)
{
	h->next = NULL;
	h->pprev = NULL;
}

static inline int hlist_unhashed(const struct hlist_node *h)
{
	return !h->pprev;
}

static inline int hlist_empty(const struct hlist_head *h)
{
	return !h->first;
}

static inline void __hlist_del(struct hlist_node *n)
{
	struct hlist_node *next = n->next;
	struct hlist_node **pprev = n->pprev;

	//WRITE_ONCE(*pprev, next);
	*pprev = next;
	if (next)
		next->pprev = pprev;
}

static inline void hlist_del(struct hlist_node *n)
{
	__hlist_del(n);
	n->next = NULL;
	n->pprev = NULL;
}

static inline void hlist_del_init(struct hlist_node *n)
{
	if (!hlist_unhashed(n)) {
		__hlist_del(n);
		INIT_HLIST_NODE(n);
	}
}

static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
{
	struct hlist_node *first = h->first;
	n->next = first;
	if (first)
		first->pprev = &n->next;
	//WRITE_ONCE(h->first, n);
	h->first = n;
	n->pprev = &h->first;
}

/* next must be != NULL */
static inline void hlist_add_before(struct hlist_node *n,
					struct hlist_node *next)
{
	n->pprev = next->pprev;
	n->next = next;
	next->pprev = &n->next;
	//WRITE_ONCE(*(n->pprev), n);
	*(n->pprev) = n;
}

static inline void hlist_add_behind(struct hlist_node *n,
				    struct hlist_node *prev)
{
	n->next = prev->next;
	//WRITE_ONCE(prev->next, n);
	prev->next = n;
	n->pprev = &prev->next;

	if (n->next)
		n->next->pprev  = &n->next;
}

/* after that we'll appear to be on some hlist and hlist_del will work */
static inline void hlist_add_fake(struct hlist_node *n)
{
	n->pprev = &n->next;
}

static inline bool hlist_fake(struct hlist_node *h)
{
	return h->pprev == &h->next;
}

/*
 * Check whether the node is the only node of the head without
 * accessing head:
 */
static inline bool
hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
{
	return !n->next && n->pprev == &h->first;
}

/*
 * Move a list from one list head to another. Fixup the pprev
 * reference of the first entry if it exists.
 */
static inline void hlist_move_list(struct hlist_head *old,
				   struct hlist_head *new)
{
	new->first = old->first;
	if (new->first)
		new->first->pprev = &new->first;
	old->first = NULL;
}

#define hlist_entry(ptr, type, member) container_of(ptr,type,member)

#define hlist_for_each(pos, head) \
	for (pos = (head)->first; pos ; pos = pos->next)

#define hlist_for_each_safe(pos, n, head) \
	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
	     pos = n)

#define hlist_entry_safe(ptr, type, member) \
	({ typeof(ptr) ____ptr = (ptr); \
	   ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
	})

/**
 * hlist_for_each_entry	- iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry(pos, head, member)				\
	for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
	     pos;							\
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
 * @pos:	the type * to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(pos, member)			\
	for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
	     pos;							\
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
 * @pos:	the type * to use as a loop cursor.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(pos, member)				\
	for (; pos;							\
	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another &struct hlist_node to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_safe(pos, n, head, member) 		\
	for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
	     pos && ({ n = pos->member.next; 1; });			\
	     pos = hlist_entry_safe(n, typeof(*pos), member))

#endif
